Anti-offsetting oil

ABSTRACT

An anti-offsetting oil including an organopolysiloxane having the formula (1) below and containing low molecular weight organopolysiloxanes having a molecular weight of 3,000 or less in a content of 50 ppm or less. ##STR1## wherein R f  &#39;s represent a perfluoroalkyl which may contain at least one ether linkage; R&#39;s represent a monovalent hydrocarbon group; Y&#39;s represent a divalent organic group having 2 to 5 carbon atoms; a represents an integer of 1 or more and b represents an integer of 0 or more, provided that a and b satisfy 3a+3b+2=15 to 4,000; and c and d are an integer of 0 to 3. This fluid has a good wettability to silicone rubber or fluorine forming the surfaces of fixing rolls of electrophotographic copying machines, and hence can effectively prevent offset. Since it contains no low-molecular weight organopolysiloxanes, the electric-contact failure may hardly occur.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a silicone fluid-based anti-offsetting oilused in fixing rolls.

2. Description of the Prior Art

In electrophotographic copying, as a method for heat fixing toner imagesformed of thermoplastic powder which have been transferred to copyingsheet, it is common to bring a heated roll into direct contact withtoner images. However, once the toner images turn viscous upon heatmelt, a part of toner images on copying sheet such as copying paper mayadhere also to the surface of the roll, so that this part of tonerimages is transferred from a first sheet to a next sheet when the nextsheet is delivered onto the roll, and simultaneously a part of viscoustoner images transferred from the next sheet adheres to the roll. Thisphenomenon is commonly called "offset" in printing techniques.

To solve this problem, a fixing roll has been conventionally used whichcomprises a core roll covered on its surface with a film having a lowsurface energy as exemplified by polytetrafluoroethylene (PTFE) film ortetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (PFA) film onwhich silicone fluid is applied in a thin film at the time of heatfixing (Japanese Post-examination Patent Publication (Kokoku) No.41-16990). In such a fixing roll, however, the roll surface has so low asurface energy that the silicone fluid applied may be repelled and nouniform coating can be formed, resulting in no sufficient anti-offseteffect. As a method for improving such a fixing roll, it is proposed touse a silicone fluid to which a fluorine-containing surfactant is added(Japanese Pre-examination Patent Publication (kokai) No. 58-11624).However, because of a poor compatibility of silicone fluid with thefluorine-containing surfactant, no stable anti-offset effect has beenachieved.

As an anti-offsetting silicone fluid, a silicone fluid having afluorine-containing organic group in the molecule is also proposed(Japanese Pre-examination Patent Publication No. 51-18544). However, nosufficient effect can be achieved unless an organopolysiloxane having along-chain fluorine-containing organic group such as a fluoroalkyl groupor a fluoropolyether group is used. However, for reasons of production,such an organopolysiloxane having a long-chain fluorine-containingorganic group can not avoid containing low-molecular weight volatilecomponents, which are causative of electric-contact failure ofelectronic devices. For example, a linear organopolysiloxane productionprocess comprising the step of subjecting a cyclotrisiloxane having along-chain fluorine-containing organic group to polymerization in thepresence of a catalyst such as concentrated sulfuric acid or activatedclay is accompanied by depolymerization reaction, and this reactionproduces as by-products volatile components such as cyclic siloxanes, inparticular, cyclic oligosiloxanes with three to tens of siloxane unitsor a low-molecular weight linear siloxane. As known in the art, when thelinear organopolysiloxane containing such volatile components is used asan anti-offsetting oil, the volatile components in thisorganopolysiloxane gradually volatilize to adhere to electric contactsand so forth to cause troubles such as contact failure. Accordingly,when the linear organopolysiloxane is used as an anti-offsetting oil,the content of the volatile components in it must be made as small aspossible. Of the above volatile components, the low-molecular weightlinear siloxanes and the cyclic siloxanes having a low degree ofpolymerization, i.e., having a low molecular weight can be removed bysubjecting the resultant polymer to stripping under reduced pressure andheating or solvent extraction. It, however, is very difficult to removecyclic siloxanes with a polymerization degree of 10 or more, inparticular, with 20 or more. When the linear organopolysiloxane whichhas been thus treated is used as the anti-offsetting oil, the troublessuch as contact failure can not be avoided because it contains asvolatile components cyclic products with a polymerization degree of 10or more and a molecular weight of not more than 3,000 in a rather largequantity.

For the above reasons, it has been sought to develop a siliconefluld-based anti-offsetting oil having a good wettability to low-surfaceenergy materials such as silicone rubber and fluorine rubber and alsocontaining no organopolysiloxane having a molecular weight of 3,000 orless including cyclic siloxanes with a polymerization degree of 20 ormore.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a silicone fluid-basedanti-offsetting oil that can be uniformly applied on the surface of afixing roll covered with a low-surface energy material such as siliconerubber or fluorine rubber, contains substantially no low-molecularweight siloxanes, and hence does not cause troubles such as offset andcontact failure.

The present inventors made extensive studies in order to solve the aboveproblems that the conventional silicone fluid-based anti-offsetting oilshave had. As the result, they took note of the fact that a linearorganopolysiloxane obtained by ring-opening polymerization offluorine-containing cyclotrisiloxane contains volatile components suchas cyclic siloxane in a small amount, and they removed volatilecomponents from this organopolysiloxane by a known method, so that alinear organopolysiloxane was found to be obtained which contained noorganopolysiloxane with a molecular weight of 30,000 or less withoutregard to straight-chain or cyclic, in particular, containedsubstantially no cyclic siloxane with 20 or more siloxane units and amolecular weight of not more than 3,000, having been hitherto difficultto remove, and also which had a good wettability to low-surface energymaterials such as silicone rubber and fluorine rubber. The presentinvention has been accomplished from such findings.

The present invention provides an anti-offsetting oil comprising asilicone fluid comprising an organopolysiloxane represented by thefollowing general formula (1) and in which an organopolysiloxane havinga molecular weight of 3,000 or less is in a content of 50 ppm or less.##STR2## wherein R_(f) 's each represent a perfluoroalkyl group having 3to 20 carbon atoms, which may contain at least one ether linkagetherein; R's are the same or different and each represent a monovalenthydrocarbon group having 1 to 15 carbon atoms; Y's each represent adivalent organic group having 2 to 5 carbon atoms; a represents aninteger of 1 or more and b represents an integer of 0 or more, providedthat a and b satisfy 3a+3b+2=15 to 4,000; and c and d are each aninteger of 0 to 3.

The anti-offsetting silicone fluid of the present invention containssubstantially no volatile components such as low molecular weight cyclicsiloxane and low-molecular weight linear siloxane, and hence does notcause the troubles such as contact failure. The present oil also shows agood wettability to low-surface energy materials such as silicone rubberand fluorine rubber, and hence can be uniformly applied on fixing rollsand can be greatly effective for improving the releasability of toners.Thus, a fixing assembly free of troubles such as electric-contactfailure and offset can be produced by incorporating the anti-offsettingoil of the present invention into the fixing assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an infrared absorption spectrum of the silicone fluid usedin the present invention, produced in Synthesis Example 1.

FIG. 2 shows an infrared absorption spectrum of the silicone fluid usedin the present invention, produced in Synthesis Example 2.

FIG. 3 shows an infrared absorption spectrum of the silicone fluid usedin the present invention, produced in Synthesis Example 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The anti-offsetting oil of the present invention comprises theorganopolysiloxane represented by the above general formula (1),provided that linear and cyclic organopolysiloxanes having a molecularweight of 3,000 or less are in a content of 50 ppm or less, preferably25 ppm or less, and more preferably 10 or less.

In the above general formula (1), the R_(f) perfluoroalkyl group isexemplified by:

a perfluoropolyether group represented by the following general formula(1a): ##STR3## wherein R¹ is --CF(CF₃)--, --CF₂ CF₂ -- or --CF(CF₃)CF₂--; and p is an integer of 1 to 5; and

a perfluoroalkyl group represented by the following general formula(1b):

    C.sub.L F.sub.2L+1 --                                      (1b)

wherein L is an integer of 3 to 20. Stated specifically, the group offormula (1a) is exemplified by ##STR4## and the group of formula (1b) isexemplified by

    F--(CF.sub.2).sub.3 --CF.sub.2 --, F--(CF.sub.2).sub.7 --CF.sub.2 and (CF.sub.3).sub.2 CF--.

In the above general formula (1), the R monovalent hydrocarbon can beexemplified by an alkyl group, in particular, an alkyl group having 1 to6 carbon atoms such as a methyl group, an ethyl group, a propyl group, apentyl group or a hexyl group; an aryl group, in particular, an arylgroup having 6 to 10 carbon atoms such as a phenyl group and a tolylgroup; an aralkyl group, in particular, an aralkyl group having 7 to 15carbon atoms such as a benzyl group or a phenylethyl group. Y representsa divalent organic group having 2 to 5 carbon atoms. Taking account ofthe fact that the anti-offsetting oil of the present invention is usedin an environment of high temperature, the Y divalent organic group maypreferably be an alkylene group or an amide linkage (--NHCO--), andparticularly preferably an ethylene group.

In the above general formula (1), the letter symbol a represents aninteger of 1 or more and b represents an integer of 0 or more, providedthat a and b satisfy 3a+3b+2=15 to 4,000; and c and d are each aninteger of 0 to 3. Of these, the degree of polymerization indicated by"3a+3b+2" may preferably be such a value that this silicone fluid mayhave a viscosity at 25° C. of from 100 to 30,000 cSt, and preferablyfrom 300 to 3,000 cSt.

In order to control the content of the volatile components such as lowmolecular weight cyclic siloxane to a lower level from the initial stageof production, the silicone fluid used in the present invention maypreferably be produced in the following manner.

Fluorine-containing cyclotrisiloxane represented by the followinggeneral formula (2): ##STR5## wherein R_(f) and R's are as defined inthe above general formula (1); and optionally cyclotrisiloxanerepresented by the following general formula (3): ##STR6## wherein R'sare as defined in the above general formula (1); are ring-openingpolymerized in the presence of a lithium silanolate catalyst, and thepolymerization product obtained is treated by heating at 100° C. orabove, under a reduced pressure of 10⁻¹ mmHg or below, and/or by solventextraction to remove volatile components from the polymerizationproduct. Thus, a silicone fluid can be obtained which is comprised ofthe organopolysiloxane represented by the general formula (1) and inwhich the organopolysiloxanes having a molecular weight of 3,000 or less(inclusive of the cyclic siloxane with 20 or more siloxane units) is ina content of 50 ppm or less.

In electrophotographic copying processes in which toner imagestransferred onto copying sheet such as copying paper are brought intocontact with a heated roll and heat fixed, the silicone fluid thusobtained is applied on the surface of the roller in the form of a thinfilm, where the offset can be prevented. The roller usually has asurface formed of silicone rubber or fluorine rubber.

EXAMPLES

Working examples of the present invention will now be given below,together with comparative examples. In the following Synthesis Examples,the viscosity is a value obtained when measured at 25° C.

Synthesis Example 1 (Silicone fluid for the present invention)

Into a 1 liter separable reaction flask with a stirrer, 1,000 g (1.458mols) of a cyclotrisiloxane represented by the formula; ##STR7## 2.27 g(0.00972 mol) of pentamethylvinylcyclotrisiloxane, 2.79 g (0.00972 mol)of lithium silanolate represented by the formula: ##STR8## and 1.0 g oftetraglyme were charged, and reaction was carried out at a temperatureof 100° C. for 5 hours in an atmosphere of nitrogen.

Next, the reaction mixture was cooled to a temperature of 50° C., and1.58 g (0.01458 mol) of trimethylchlorosilane and 3.55 g (0.022 mol) ofhexamethyldisilazane were introduced into it, followed by stirring for 2hours to effect neutralization. Thereafter, vacuum stripping was carriedout at a temperature of 150° C., and then the salt formed was filteredto obtain 952 g of an organopolysiloxane (viscosity: 14,150 cSt).

Next, this product was passed through a thin-film type moleculardistillation still under conditions of 270° C. and 1×10⁻⁴ mmHg to obtain926 g of an organopolysiloxane (viscosity: 15,010 cSt).

Next, to determine cyclic polysiloxanes having a molecular weight notmore than 3,000 contained in the organopolysiloxane thus produced, 1.0 gof the organopolyxane and as the internal standard 10.0 g of acetonecontaining 20 ppm of n-decane were put in a lidded glass bottle,followed by shaking, and thereafter the resultant mixture was allowed tostand for 24 hours. The polysiloxanes thus extracted to the acetonephase were determined by gas chromatography using a flame ionizationdetector (FID). The cyclic siloxanes detected were in a content of 1 ppmor less. The amount of linear siloxanes was below the detectable limit.The upper limit of the molecular weight of cyclic siloxanes detectableby means of FID is about 3,000. Therefore, the content of the siloxaneswith a molecular weight of 3,000 or less can be considered as 1 ppm orless. The measurement above was performed under conditions shown below.

Instrument Used

GC-14A, manufactured by Shimadzu corporation

Column

Capillary column TC-1701 0.53 mm×30 mm, manufactured by GL

Temperature Program

Initial temperature: 70° C. (1 min.);

rate of temperature rise: 15 K/min.; final

temperature: 270° C. (retention time: 40 min.)

Infrared absorption spectrum and ¹ H-NMR spectrum of theorganopolysiloxane finally obtained as above were also measured toobtain the following results.

Infrared absorption spectrum: as shown in FIG. 1

Characteristic absorption

990 to 1,130 cm⁻¹ (Si--O--Si)

2,970, 1,260, 810 cm⁻¹ (Si--CH₃)

1,000 to 1,450 cm⁻¹ (C--F)

¹ H-NMR (freon 113 solvent)

0.76 to 1.60 ppm (m --CH₂ --Si--2H)

1.83 to 2.81 ppm (m --CH₂ --CF--2H)

0.21 to 0.52 ppm (m --CH₃ --Si--15H)

From the above results, the organopolysiloxane obtained was confirmed tobe a linear organopolysiloxane represented by the following averagemolecular formula: ##STR9##

Synthesis Example 2 (Silicone fluid for the present invention)

Into a 2 liter separable reaction flask with a stirrer, 916.4 g (1.40mols) of cyclotrisiloxane represented by the formula: ##STR10##

1,468.5 g (6.60 mols) of hexamethyltrisiloxane, 1,104.0 g oftetrahydrofuran (THF) and 191.1 g (0.20 mol) of a 30% by weight THFsolution of lithium silanolate represented by the formula: ##STR11##were charged, and reaction was carried out at 25° C. for 5 hours in anatmosphere of nitrogen.

Next, at this temperature, 32.6 g (0.30 mol) of trimethylchlorosilaneand 72.6 g (0.45 mol) of hexamethyldisilazane were introduced into it,followed by stirring for 2 hours to effect neutralization.

Thereafter, vacuum stripping was carried out at 150° C., and then thesalt formed was filtered off to obtain 2,316.0 g of anorganopolysiloxane (viscosity: 374 cSt).

Next, this product was passed through a thin-film type moleculardistillation still under conditions of 270° C. and 1×10⁻⁴ mmHg to obtain2,231.7 g of an organopolysiloxane (viscosity: 399 cSt).

Cyclic polysiloxanes with a molecular weight not more than 3,000 in thisorganopolysiloxane were determined in the same manner as in SynthesisExample 1 to reveal that the cyclic siloxanes were in a content of 25ppm.

Infrared absorption spectrum and ¹ H-NMR spectrum of theorganopolysiloxane finally obtained as above were also measured toobtain the following results.

Infrared absorption spectrum: as shown in FIG. 2

Characteristic absorption (cm⁻¹)

980 to 1,100 (Si--O--Si)

2,965, 1,265, 810 (Si--CH₃)

1,000 to 1,430 (C--F)

¹ H-NMR (freon 113 solvent)

0.70 to 1.50 ppm (m, --CH₂ Si--2H)

1.75 to 2.67. ppm (m, --CH₂ CF--2H)

0.20 to 0.47 ppm (m, --CH₃ Si--99H)

From the above results, the organopolysiloxane obtained was confirmed tobe a linear organopolysiloxane represented by the following averagemolecular formula: ##STR12##

Synthesis Example 3 (Silicone fluid for comparison)

Into a 2 liter separable reaction flask with a stirrer, 837.9 g (1.28mols) of a cyclotrisiloxane represented by the formula: ##STR13## 712.0g (3.20 mols) of hexamethyltrisiloxane and 49.7 g (0.16 mol) ofdecamethyltetrasiloxane were charged, and 0.16 g oftrifluoromethanesulfonic acid was further added in an atmosphere ofnitrogen, to carry out reaction at 50° C. for 12 hours.

Next, at this temperature, 77.5 g (0.48 mol) of hexamethyldisilazane wasadded, followed by stirring for 2 hours to effect neutralization.

Thereafter, vacuum stripping was carried out at 150° C., and then thesalt formed was filtered off to obtain 1,534.6 g of anorganopolysiloxane (viscosity: 179 cSt).

Next, this product was passed through a thin-film type moleculardistillation still under conditions of 270° C. and 1×10⁻⁴ mmHg to obtain1,285.0 g of an organopolysiloxane (viscosity: 238 cSt).

Cyclic polysiloxanes with a molecular weight not more than 3,000 in thisorganopolysiloxane was determined in the same manner as in SynthesisExample 1 to reveal that the cyclic siloxanes were in a content of 3,980ppm.

Infrared absorption spectrum and ¹ H-NMR spectrum of theorganopolysiloxane finally obtained were also measured to obtain thefollowing results.

Infrared absorption spectrum: as shown in FIG. 3

Characteristic absorption (cm⁻¹)

980 to 1,100 (Si--O--Si)

2,960, 1,265, 805 (Si--CH₃)

1,010 to 1,420 (C--F)

¹ H-NMR (ppm; freon 113 solvent)

0.68 to 1.50 (m, --CH₂ Si--2H)

1.76 to 2.69 (m, --CH₂ CF--2H)

0.19 to 0.45 (m, CH₃ Si--93H)

From the above results, the organopolysiloxane obtained was confirmed tobe a linear organopolysiloxane represented by the following averagemolecular formula: ##STR14##

Example 1

With regard to the organopolysiloxanes produced in Synthesis Examples 1and 2, contact angles of their samples at 25° C. on a PFA film weremeasured by the droplet method using a contact angle meter (CA-DT TypeA, manufactured by Kyowa Kaimen Kagaku K. K.). The wettability withrespect to the value of contact angle was evaluated as;

A: Good wettability (contact angle: less than 10°).

C: Poor wettability (contact angle: 10° or more).

The results of evaluation were as shown in Table 1.

Example 2

With regard to the organopolysiloxanes produced in Synthesis Examples 1and 2, releasability of toner was evaluated in the manner shown below.

(1) On the surface of a 50 μm PFA film stuck to a silicone rubber piece(1 cm×5 cm, 2 mm thick), about 50 mg of a sample is dropped, and coatedusing absorbent cotton in the form of thin film.

(2) Black toner is uniformly placed on one side of PPC paper (1 cm×5cm), and the sample-coated surface of the rubber piece of (1) and thetoner side of the paper are superposingly put together.

(3) The matter put together in (2) is pressed using a heat pressingmachine (TP-701S sheet seal tester, manufactured by Tester Sangyo K. K.)under conditions of 200° C., 4 kg/cm² and 5 seconds.

(4) The test piece thus obtained in (3) is cooled to room temperature(25° C.). Thereafter, the PPC paper is peeled off and the quantity oftoner remaining on the rubber piece is visually observed.

The releasability of toner was evaluated as;

A: Almost no toner remains on the rubber piece surface.

C: Toner remains on the rubber piece surface in a rather large quantity.

The results of evaluation were as shown in Table 1.

Example 3

With regard to the organopolysiloxanes produced in Synthesis Examples 1and 2, the electric-contact failure was evaluated in the manner shownbelow.

(1) A 90 mm diameter glass Petri dish containing 10 g of a sample and aDC motor (LC20-129, manufactured by Koparu Denshi K. K.) are placed in a4 liter volume container made of metal and the container is hermeticallysealed.

(2) The metal container of (1) is put in a 60° C. thermostatic chamber,and the motor is electrified to set it driving.

(3) The time period from the start to the stop of the motor is recorded.

The electric-contact failure was evaluated as;

A: Motor does not stop for 100 hours or longer.

C: Motor stops within a time shorter than 50 hours.

The results of evaluation were as shown in Table 1.

Comparative Example 1

The wettability, releasability of toner and electric-contact failurewere evaluated in the same manner as in Examples 1 to 3 except for usingthe organopolysiloxane produced in Synthesis Example 3.

The results of evaluation were as shown in Table 1.

Comparative Example 2

The wettability, releasability of toner and electric-contact failurewere evaluated in the same manner as in Examples 1 to 3 except for usinga commercially available dimethylpolysiloxane (viscosity at 25° C.: 300cSt; available from Shin-Etsu Chemical Co., Ltd.).

The results of evaluation were as shown in Table 1.

                  TABLE 1    ______________________________________                                 Electric-            Wettability                       Releasability                                 contact            to PFA     of toner  failure    ______________________________________    Example 1 A            A         A    Example 2 A            A         A    Comparative              A            A         C    Example 1    Comparative              C            C         C    Example 2    ______________________________________

As described above, the anti-offsetting oil of the present invention hasgood wettability to PFA and good releasability of toner, and besides hasa very low possibility of causing the electric-contact failure which ispeculiar to silicone fluids. Thus, the present anti-offsetting oil isseen to be suitable.

What is claimed is:
 1. An anti-offsetting oil, comprising anorganopolysiloxane having the formula (1): ##STR15## wherein Rrepresents a monovalent hydrocarbon group having 1 to 15 carbon atoms,which are the same or different; Y represents a divalent organic grouphaving 2 to 5 carbon atoms, which are the same or different; arepresents an integer of 1 or more, and b represents an integer of 0 ormore, provided that a and b satisfy:

    3a+3b+2=15 to 4,000

and wherein c and d is each an integer of 0 to 3, and anorganopolysiloxane having a molecular weight of 3,000 or less is presentin an amount of 50 ppm or less; and wherein R_(f) is aperfluoropolyether group having the formula (1a): ##STR16## wherein R¹is --CF(CF₃)--, --CF₂ CF₂ -- or --CF(CF₃)CF₂ --; and p is an integer of1 to 5; or a perfluoroalkyl group having the formula (1b):

    C.sub.L F.sub.2L+1 --                                      (1b)

wherein L is an integer of 3 to
 20. 2. The anti-offsetting oil of claim1, wherein said organopolysiloxane having a molecular weight of 3,000 orless is present in an amount of 25 ppm or less.
 3. The anti-offsettingoil of claim 1, wherein said organopolysiloxane having a molecularweight of 3,000 or less is present in an amount of 10 ppm or less. 4.The anti-offsetting oil of claim, 1 wherein R_(f) is a group representedby: ##STR17##
 5. The anti-offsetting oil of claim 1, wherein themonovalent hydrocarbon represented by R in the formula (1) is an alkylgroup having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbonatoms, or an arylalkyl group having 7 to 15 carbon atoms.
 6. Theanti-offsetting oil of claim 1, where Y in the formula (1) is anethylene group or an amide linkage.
 7. The anti-offsetting oil of claim1, wherein R in the formula (1) is an alkyl group selected from thegroup consisting of methyl, ethyl, propyl, pentyl and hexyl.
 8. Theanti-offsetting oil of claim 1, wherein R in the formula (1) is an arylgroup selected from the group consisting of benzyl and phenethyl.
 9. Theanti-offsetting oil of claim 6, wherein Y in the formula (1) is analkylene group and is an ethylene group.
 10. The anti-offsetting oil ofclaim 1, wherein a degree of polymerization indicated by 3a+3b+2 is suchthat the organopolysiloxane has a viscosity at 25° C. of from 100 to30,000 cSt.
 11. The anti-offsetting oil of claim 10, wherein a degree ofpolymerization indicated by 3a+3b+2 is such that the organopolysiloxanehas a viscosity at 25° C. of from 300 to 3,000 cSt.
 12. Anelectrophotographic copying process comprising bringing a heated rollinto contact with a toner image transferred onto copying sheet to heatfix the toner image, wherein said roll has a surface formed of asilicone rubber or a fluorine rubber, and the anti-offsetting fluidaccording to claim 1 is applied in a thin film on the surface.
 13. Theprocess according to claim 12, wherein said organopolysiloxane having amolecular weight of 3,000 or less is present in a content of 25 ppm orless.
 14. The process according to claim 12, wherein saidorganopolysiloxane having a molecular weight of 3,000 or less is presentin a content of 10 ppm or less.
 15. The process according to claim 12,wherein the R_(f) in the formula (1) is a group represented by ##STR18##16. The process according to claim 12, wherein the monovalenthydrocarbon represented by R in the formula (1) is an alkyl group having1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms or anaralkyl group having 7 to 15 carbon atoms.
 17. The process according toclaim 12, wherein the Y in the formula (1) is an ethylene group or anamide linkage.